Bone fixing device for cranial surgery

ABSTRACT

The device comprises a body of elastic characteristics with two end zones and an intermediate connection zone of same, one of the end zones having an aperture for its incorporation in the edge of the bone segment or bone flap separated in the operation, whereas the other end has cap means over the rest of the cranium, in order to limit the dropping of the bone segment in its new placement in the aperture made in the cranium and the intermediate part of the device being that which joins the two ends, an elastic part transversally which thereby remains housed in the separating interstice between the separated bone segment and the cranium and which permits the device to adjust to the width of the interstice made in the cutting operation in the surgical operation.

The present invention is aimed at disclosing a bone fixation device forcranial surgery which presents numerous advantages regarding the knownart.

It is well-known that after a craniotomy and the resulting brainsurgery, the bone element that has been separated in order to haveaccess to the part to be operated on, which is also known as “boneflap”, must again be placed and fixed in the cranium. The reason forthis is not just cosmetic, but is also to improve the safety of thebrain and thus, the patient. The visible bone defects can causepsychosocial rejection and also the danger of permanent damage of amechanical nature in the brain.

Thus, the fixation systems of the bone element separated in theoperation must not only ensure fixation, but also permit a bonegrowth-healing that avoids pseudoarthrosis.

Formerly, the fixation of the bone element separated in the operationwas carried out using wires, and subsequently, by non-reabsorbable bonefixations.

Mechanically, bone fixations are not secure enough as regards theirfixing power to the cranium because there is just one low-degreefriction force connection. For this reason, frequent problems have beenobserved, such as bone flap dislocations, with depressions orprotrusions from this.

Afterwards, cranial fixation miniplates appeared, which, even thoughthey improved the quality of the fixation, were cumbersome to place.

A system known as CranioFix has also been developed consisting of twoconcave disks, which are assembled on a fine shaft that joins both diskswhen they are brought together by means of an applicator. The basicadvantage of this system is that it is designed in such a way that itcan cover the trephine hole. However, placement is also difficult andcan give rise to complications of an epidural bleeding nature, duraltears and so on.

In order to solve the drawbacks of the previously known systems, theinventor has carried out research to develop a new fixation device forthe bone element separated during the operation (craniotomy) which actson the spongy part of the cranial bone by exerting pressure on thelongitudinal direction of this bone, as if it were a “spring” or “wedge”between the bone flap of the craniotomy and the cranium.

Essentially, the device object of the invention, presents a clip-likestructure, provided with elastic features and which has fixating meansin the edge of the bone element separated in the operation, and for itssupport in the opposite edge of the cranium from which said bone or“flap” element of the craniotomy has been separated. In a preferredembodiment, the device will be made up of a clip made of fine, thintitanium plate or other metal alloys, or even synthetic materials, whichpresent an appreciably U-shaped structure intended for inserting intothe edge of the bone element separated in the operation and which, atthe other end, has a tab intended for resting on the opposite part ofthe cranium, said end zones being joined by an intermediate zone withelastic features, for example, a V-shaped or similar structure. In thisway, the device can be well fixated in the bone element, or “bone flap”separated in the operation and is thereby arranged end to end over theopposite end of the aperture made in the cranium, in order to prevent,in so far as is possible, the vertical movement of said bone element.

The number of bone fixation devices used in a craniotomy operation willvary, usually being evenly distributed along the periphery of the boneflap.

The bone fixation device object of the invention offers the advantagesof carrying out the craniotomy support in a non-traumatic way, in thesense that it is not necessary to make new perforations in the bone(both of the craniotomy and of the rest of the cranium bone), nor is itnecessary that it takes up the cranium epidural space, which can causedural tears and/or epidural haematomas. It is equally resistant topressure and does not permit dislocations of the flap. Also, it permitsthe placement, and subsequent bone regeneration-growth, in the spacemade by the craniotomy.

Furthermore, the advantage of the device object of the present inventionis its great speed and simplicity of placement as regards the currentlydisclosed systems. In the same way, in the event of a new operation, itcan be withdrawn easily since its elastic mechanism or “spring” featuresmean that it can be separated by a simple lever action with the minimumof effort and thus make possible its subsequent re-use.

According to an additional embodiment of the present invention, the bonefixation device is made up of a single laminar element, exclusively forcutting and bending operations, as well as mechanical or other types oftreatment in order to achieve greater roughness in certain areas.Therefore, this bone fixation device comprises a generally “U”-shapedelement whose intermediate section and part of one of the two paralleltabs have a spacious aperture or window, the material of which haspartly separated in the form of an angled side, which determines a stepopposite the “U” shaped zone, intended for resting on the cranium boneinto which the aperture has been performed.

The horizontal support surfaces with the separated bone segment and withthe upper face of the edge of the aperture made in the cranium have aspecial finish for achieving greater fixation and enhancedosseointegration in the corresponding bone parts, having thus preferablybeen achieved, in accordance with the improvements herein, by means ofmicroteeth.

Several representative drawings of preferred embodiments of the presentinvention are hereby attached for greater understanding, by way ofexplanatory, but non-limiting example.

FIG. 1 shows in diagrammatic form the combination of elements in acraniotomy operation with the bone fixation device of the presentinvention.

FIG. 2 shows the first stage of the craniotomy diagrammatically.

FIG. 3 shows, in diagrammatic form, the bone flap placement operation bymeans of the bone fixation device object of the present invention.

FIGS. 4 and 5 both show details of the device object of the inventionassembled after a craniotomy.

FIG. 6 shows a plan view of a coupling zone of the device.

FIGS. 7 to 11 show different embodiments, by way of example, of the bonefixation device object of the present invention.

FIG. 12 shows a perspective view of a bone fixation device whichincorporates the enhancements of the present invention.

As can be observed in FIG. 1, the device object of the present inventionis intended in its application for a cranial operation in which, fromthe cranium -1- a fragment or “bone flap” -2- is separated after makingthe aperture determining the face of cut -3-. For the replacement of thebone fragment -2- in the previously made aperture, for the purposes ofpermitting the subsequent bone fixation, the present invention envisagesthe embodiment of a bone fixation device -4- with elastic features,having means for its smooth fixating in the edge -5- of the bonefragment -2- and for establishing a cap over the upper surface -6- ofthe cranium next to the aperture -3-.

As represented in FIGS. 7 to 11, the device -4- will preferably presenta fixation zone in the edge -5- that will preferably comprise twoappreciably U-like parallel arms -7- and -8- intended for clamping theedge of the bone fragment, as has been represented in FIGS. 1, 3, 4 and5, said device -4- also comprising, in the opposite end to said couplingzone by means of the arms -7- and -8-, a tab -9- intended forestablishing contact and thereby serving as a cap for arranging the bonefragment -2- appreciably at the same height as the zone -6- of thecranium next to the aperture of the intervention, the two ends of thedevice being linked by an intermediate zone -10- with elastic features,for example, by means of the elements -11- and -12- which adopt a V orother shape, with the possibility of lateral compression, as shown inFIG. 9, wherein transversal pressure -13- causes the drawing together ofthe arms -11- and -12-, and inversely, once the device has been placed,the elastic action will tend to apply the vertical side -14- ofseparation of the arms -7- and -8- against the surface of the cut -3-.

For better adaptation, it will be possible to make the device indifferent heights, thereby permitting the operator to select the mostsuitable. In FIG. 8 a second element -15- has been represented in whichthe height h between the fixating arms -16- and -17- to the bone segmentis less than the height H of the embodiment shown in FIG. 4.

As is evident, what is essential to the device object of the inventionis the constitution of same with elastic features, presenting onecoupling end at the edge of the bone segment separated from the craniumin the intervention and another end with the possibility of a cap overthe upper surface of the cranium in the vicinity of the aperture madetherein, presenting, moreover, elastic features for absorbing thetransversal play. As is obvious, the need to absorb said transversalplay can also be justified by the possible variability of the intersticethat has occurred because of the operation between the bone element or“bone flap” -2- and the aperture -3-.

In FIGS. 10 and 11, embodiment examples are shown, it being observed inthe case of FIG. 10 that the device -18- has two arms -19- and -20- bothfitted with protuberances -21- and -22- for enhanced support on theupper and lower faces of the bone segment -2-, whereas in FIG. 11, thedevice -23- presents on its arms -24- and -25- bending -26- and -27- forcontact with the upper and lower surface of the bone segment. Thesearrangements can also permit the support arms in the bone segment, suchas -7- and -8- or even -19- , -20-; -24-, -25- to exert a certainelastic action on the upper and lower faces of the bone segment, therebypermitting a better adaptation to the thickness of same.

Therefore, in a craniotomy operation one will first of all proceed toseparating the bone segment -2- from the rest of the cranium -1-, asshown in FIG. 2, thereby producing an interstice -28- wherein the bonefixation devices shall be subsequently incorporated, as has beenrepresented in FIGS. 3 to 5, wherein it is also observed that in a firststage, the fixation devices according to the present invention, such as-29- and -30-, can receive lateral pressures, represented by the vectors-31- and -32-, for permitting the coupling of the bone segment -2- inthe cranium aperture, except for the interstice -28-.

In the additional embodiment which has been shown in FIG. 12, the bonefixation element presents a generally “U” structure with two parallelarms -101- and -102- and an intermediate connection arm -103- from thefirst, it being a feature that the intermediate arm -103- and a goodpart of one of the parallel arms -102- has a large aperture wherefrom ithas separated by partial cutting of the angled side -104-, and presentsan arm -105- forming an acute angle with the intermediate arm from theelement in “U” -103- and an upper arm bent parallel to the elements-101- and -102- from the element in “U”, having been represented in thedrawing with the number -106-.

By means of this set up, the same results envisaged in the main patentare achieved, clamping the edge of the bone segment separated from thecranium through the arms of the “U” -101- and -102-, and resting on theupper face of the cranium bone in which the surgical aperture has beenmade, the end -106- of the angled part -104-.

The partial cut of the angled side -104-, which has been shown by way ofa rectangular-shaped example, determines a connecting zone -110- withthe rest of the part.

In order to improve the device's grip on the bone elements, the contactfaces of elements -101- and -102- parallel to each other, indicated withthe numbers -107- and -108-, as well as the lower face of the horizontalpart -106-, indicated with the number -109-, have a finish which allowsa greater gripping with the bone, done in any technically known way, forexample, with microteeth. Nevertheless, said finish could consist ofzones attacked by means of acid, or subject to sand granulating or ofother elements, in order to get a finish with surface craters to obtaingreater adherence, or any other known method technically appropriate toit.

1.- Bone fixation device for cranial surgery, characterized in that itcomprises a body of elastic characteristics with two end zones and anintermediate connection zone of same, one of the end zones having anaperture for its incorporation in the edge of the bone segment or boneflap separated in the operation, whereas the other end has cap meansover the rest of the cranium, in order to limit the dropping of the bonesegment in its new placement in the aperture made in the cranium and theintermediate part of the device being that which joins the two ends, anelastic part transversally which thereby remains housed in theseparating interstice between the separated bone segment and the craniumand which permits the device to adjust to the width of the intersticemade in the cutting operation in the surgical operation. 2.- Bonefixation device for cranial surgery, according to claim 1, characterizedin that the fixating end in the bone segment separated in the operationhas two arms intended for establishing contact with the upper face andthe lower face next to the edge of the bone segment or bone flap. 3.-Bone fixation device for cranial surgery, according to claim 2,characterized in that the arms appreciably parallel to each other. 4.-Bone fixation device for cranial surgery, according to claim 2,characterized in that the arms are flexible to permit their enhancedadaptation to different thicknesses of the bone segment or bone flap.5.- Bone fixation device for cranial surgery, according to claim 3,characterized in that the arms have protruding zones near their ends fortheir enhanced adaptation over the upper and lower faces of the bonesegment or bone flap. 6.- Bone fixation device for cranial surgery,according to claim 1, characterized in that the cap of the device overthe zone of the cranium next to the aperture of the operation is made upof a protruding tab. 7.- Bone fixation device for cranial surgery,according to claim 1, characterized in that the intermediate zonebetween the ends of the device of elastic characteristics, adopts a V orsimilar shape. 8.- Bone fixation device for cranial surgery, accordingto claim 1, characterized in that the constitution of the device is bymeans of a single laminar element bent into a “U” shape, theintermediate arm thereof and part of one of parallel arms having a largeaperture, the material of which has been partly cut, leaving aconnecting zone with the rest, thereby forming a slightly incliningangular element as regards the intermediate arm of the “U” and which hasan upper tab parallel to the parallel arms of the “U”, intended forresting on the upper face of the aperture performed surgically in thecranium. 9.- Bone fixation device for cranial surgery, according toclaim 8, characterized in that the faces in contact with the bone of theparallel arms of the element in “U” and of the flap of the angularelement have a highly adherent finish. 10.- Bone fixation device forcranial surgery, according to claim 9, characterized in that the highlyadherent finish consists of microteeth.